There is one other cause for wandering. The REAR wheels may be out of alignment and cause wandering and tracking problems. Have they been checked? If after I fix something and it Still has a problem, I assume the problem is elsewhere and determine what else affects the performance of the issue in question. What about the motor and transmission mounts? If they are defective, alignments will be off after a while due to misalignment of the trans. connections etc. (I'm guessing here, not familiar with the Focus front design). The point is, what else have they checked?